Synthetic-fiber felts useful as filters are known, e.g., from U.S. Pat. No. 2,910,763 as are such felts containing PTFE fibers, e.g., from U.S. Pat. Nos. 2,893,105 and 2,933,154. U.S. Pat. No. 2,893,105 suggests the possibility of blending PTFE fibers with other fibers, inter alia, glass. Filters containing PTFE fibers are advantageous because they have outstanding resistance to high temperatures, chemical attack and abrasion. However, commercially available filters containing these fibers often permit passage of more particulate matter than is desirable under today's increasingly rigorous environmental standards.
This invention provides an intimate blend of poly(tetrafluoroethylene) and glass fibers which in the form of felts provides markedly reduced leakage while maintaining high permeability to gas flow. In addition, the felts show reduced blinding in use, are readily cleaned and exhibit remarkable resistance to wear within the claimed blend levels.